Dual flexible lip extrusion apparatus

Abstract: An extrusion apparatus includes first (102) and second (104) die body portions each having a main body (106) and a lip (108) interconnected with the main body (106) wherein the die body (102,104) portions are joined such that a single die outlet (120) is formed between and bounded by the lips. The apparatus also includes suitable structure (124) for moving the lips to adjust the die outlet (120).

Description: Technical Field The present invention relates to an extrusion apparatus for extruding a single stream of thermoplastic material according to the precharacterising part of claim 1. Background Art Dies for extruding thermoplastic material typically include a pair of die portions joined together to define an outlet through which molten thermoplastic material is extruded. Specifically, each die portion includes a lip, and the lips of the two die portions cooperate to define a die outlet or lip gap. In one type of prior art extrusion apparatus, the lips are integral with the die portions and a first one of the lips is joined to a respective die portion by a flexible hinge. Apparatus is provided to adjust the position of the first lip and thus the width of the lip gap. Specifically, the adjustment apparatus includes a plurality of thermally responsive members spaced along the width of the die and a plurality of heater elements each disposed in heat-transfer relationship with a thermally responsive member. The heater elements are individually controlled to adjust the profile of the lip gap at one edge thereof. Alternatively, a manually operable adjustment apparatus may be provided to adjust the width of the lip gap. In either case, the adjustability of the die is limited by the deflection limit of the flexible hinge. Also, the initial set-up procedure to preset the desired outlet width can be undesirably time consuming. In another prior art extrusion die, referred to as a "sliding lip" die, first and second die lip members are separate from and carried by respective die portions. The first die lip member is rigidly secured to the die body while a second die lip member is mounted for sliding movement relative to the first die lip member. Again, adjustment apparatus is provided for positioning the second die lip member so that a desired lip gap width is achieved and maintained. While this die design has a wide adjustment range, changing of the gap width can be a lengthy process and gauge control capability is limited. A third prior art extrusion die includes first and second die body portions, one having a first lip coupled integrally therewith by a flexible hinge and the other having a second, removable lip bolted thereto. A plurality of thermally responsive members are coupled to the first lip for adjusting the position of that lip to achieve a desired extrudate profile. The removable lip, on the other hand, is stationary but can be replaced by other lip members having different dimensions so that the base lip gap can be selected as desired or necessary. This die has relatively good gauge control compared with other prior art die designs but requires a longer time to change the base lip gap and thus has a longer product changeover time. Because processors of extruded film, sheet, and coatings often must meet their customers' demands with "just-in-time" deliveries, it is important that the time required to adjust the lip gap dimensions of extrusion dies be kept as short as possible to maximize production of extruded materials and minimize production of scrap material during changeovers. Moreover, because extruded materials are often required in a wide range of thicknesses, it is desirable to provide a single die having a wide adjustment range so that a variety of material thicknesses can be produced without the need to replace the lips or other components of the die and requiring minimal reconfiguration time. Document GB-A-2 028 228 (D1) discloses an extrusion die, comprising first and second die body portions, each having a main body and a lip interconnected to the main body, wherein the die body portions are joined such that a single die outlet is formed between and bounded by the lips and irst and second moving means coupled to the first and second die body portions for moving the lips to adjust the die outlet. EP-A-0 456 176 discloses an extrusion apparatus having a mechanism for thermally-controlled lip gap adjustment. The apparatus includes a flow path for a gaseous cooling medium in which flow path a plurality of temperature-responsive adjustment members are disposed. US-A-3 380 610 discloses an extrusion apparatus for rubber products, whereby the die opening is adjusted by measuring the configuration and then comparing the measured results with a standard configuration. US-A-1 422 356 discloses an extrusion apparatus whereby the die opening may be adjusted from time to time by using specific die plates according to requirement. The invention relates to a device as per GB-A-2 028 228, which forms the preamble of claim 1 on file. It is the object of the invention to provide an extrusion apparatus comprising an adjustment mechanism by which it is possible to achieve the desired lip adjustment, i.e. the gap between the two lips of the apparatus rapidly, easily and as exactly as possible. This object is achieved by an extrusion apparatus as defined in claim 1. Particular embodiments of the invention are the subject of the dependent claims 2 and 3. US-A-3 264 686 relates to the same type of equipment, i.e. an extrusion apparatus for extruding of a stream of plastic material. Also, there are two lips forming an outlet. Still further, there are means for adjusting the said outlet to thereby control the thickness of the stream of plastic material. This document, however, comprises differences, which are significant. Those differences are as follows: While the extrusion apparatus as per the invention comprises a separate lip adjustment block which provides for a deformation of the lip, there is no such lip adjustment block to be found in the document. Instead, with the known device, the lip is formed by the said jaw 14 respectively 10 as outlined above. Further, the extrusion apparatus as per the invention comprises a hinge. Such hinge allows deformation of body portions carrying the lips. There is no such hinge with the document, and accordingly, there is no deformation. Instead, jaw 10 respectively 14 just make a simple movement without any deformation. Brief Description of the Drawings Fig. 1 comprises a sectional view of a prior art extrusion apparatus having a single flexible lip; Fig. 2 comprises a sectional view of a prior art extrusion apparatus having a sliding lip; Fig. 3 comprises a sectional view of a prior art extrusion apparatus having a flexible first lip and a removable second lip; Fig. 4 comprises a perspective of an extrusion apparatus according to the present invention; Fig. 5 comprises a sectional view of the extrusion apparatus of the present invention taken generally along the lines 5-5 of Fig. 4; Fig. 6 comprises a fragmentary exploded isometric view of a portion of the extrusion apparatus of Fig. 4; Fig. 7 comprises a fragmentary elevational view, partly in section and taken generally along the lines 7-7 of Fig. 4, of a portion of the extrusion apparatus of Fig. 4; Fig. 8 comprises a fragmentary sectional view, similar to Fig. 5, of a alternative embodiment of an extrusion apparatus according to the present invention; Fig. 9 comprises a fragmentary exploded isometric view, partly in section and similar to Fig. 6, of the embodiment of Fig. 8; and Fig. 10 comprises a fragmentary elevational view, partly in section and similar to Fig. 7, of the embodiment of Fig. 8. Description of the Preferred Embodiments Referring initially to Fig. 1, a prior art extrusion die 20 includes first and second die body portions 22, 24 having respective lips 26, 28. The first and second die body portions 22, 24 are joined together in any conventional manner, for example by body bolts (not shown), such that a die outlet 30 is formed between and defined by the lips 26, 28. The lips 26, 28 are integral with the die body portions 22, 24, respectively, and the lip 26 is interconnected with a main body 32 of the die body portion 22 by a hinge 34. A number of thermally expandable bolts 36 are coupled between the main body 32 and the lip 26 of the die body portion 22 for moving the lip 26 relative to the lip 28 to adjust the die outlet 30. A plurality of heaters (not shown) are disposed in heat-transfer relationship with the bolts 36 and are controlled so that the die outlet 30 has a predetermined profile corresponding to the desired dimensions of the material to be extruded. Due to the limited flexibility of the hinge 34, however, this type of die, called a flex-lip die, can produce only a limited range of extrudate thicknesses. Moreover, this design requires a long time to preset the required gap dimensions. Referring now to Fig. 2, another prior art extrusion die 40 includes first and second die body portions 42, 44 and lip members 46, 48 coupled to the die body portions 42, 44, respectively. The die body portions 42, 44 are joined such that a die outlet 50 is formed between the lip portions 46, 48. One lip member 46 is capable of sliding in a horizontal direction (as shown in Fig. 2) relative to the other lip member 48, which is bolted in place and thus remains stationary, in order to vary the dimensions of the die outlet 50. While this so-called sliding lip die has a wider operating range than the flex-lip die of Fig. 1, the sliding lip die requires a long time to change the dimensions of the die outlet 50. Moreover, this is a cumbersome die design that offers little flexibility and only limited gauge control capability. Referring now to Fig. 3, a third prior art extrusion apparatus 60 includes first and second die body portions 62, 64. The die body portion 62 includes a main body 66, a lip 68, and a hinge 70 interconnecting the main body 66 and the lip 68. The die body portion 64 includes a main body 72 and a lip member 74 secured to the main body 72 by a plurality of bolts 76 (only one of which is shown in Fig. 3). The die body portions 62, 64 are joined such that a die outlet 78 is formed between and defined by the lip 68 and the lip member 74. Thermally expandable bolts 80 coupled between the main body 66 and the lip 68 are operable to move the lip 68 to adjust the die outlet 78. In addition, the lip member 74 may be removed from the main body 72 of the die body portion 64 by unscrewing bolts 76, one of which is shown in Fig 3. A different lip member 74 may be attached to the main body 72 by the bolts 76 so that a different configuration or lip gap for the die outlet 78 is obtained. Referring now to Figs. 4 and 5, an extrusion apparatus 100 in accordance with the present invention includes first and second die body portions 102, 104. The die body portion 102 includes a main body 106, a lip 108, and a hinge 110 interconnecting the lip 108 with the main body 106. Similarly, the die body portion 104 includes a main body 112, a lip 114, and a hinge 116 interconnecting the lip 114 with the main body 112. The die body portions 102, 104 are joined by body bolts (not shown) such that a single die outlet 120 is formed between and bounded by the lips 108, 114. Mechanically adjustable bolts 122 are coupled between the main body 106 and the lip 108 for moving the lip 108 bidirectionally to precisely adjust the dimensions of the die outlet 120. Alternatively, the bolts 122 may be thermally expandable and a series of heaters (not shown) may be automatically controlled to adjust the dimensions of the die outlet 120 as disclosed in Nissel U.S. Patent No. 3,940,221, the disclosure of which is hereby incorporated herein by reference. Referring also to Figs. 6 and 7, apparatus 124 is provided for moving the lip 114 to further adjust the die outlet 120. Specifically, a sliding angle member 126 having one or more angled cam blocks 128 extending therefrom is disposed closely within a longitudinally extending recess 130 in the die body portion 112. A lip adjustment block 132 is adjustably secured by a series of shouldered bolts 134 (one of which is shown in Fig. 5) to the main body 112. More specifically, each shouldered bolt 134 is disposed in an elongated slot 136 in the lip adjustment block 132 and is threaded into a corresponding bore 137 in the main body 112. Each slot 136 is sized relative to the bolt 134 located therein such that the shouldered bolts 134 hold the block 132 against the main body 112, and the block 132 is movable up and down but not in and out (as shown in Fig. 5). Thus, the block 132 may be located in any desired position relative to the main body 112. A flange 138 carried by the lip 114 extends the full width of the die body portion 104 and is snugly disposed in a complementarily shaped groove or recess 140 formed in a marginal portion 142 extending the full width of the lip adjustment block 132. It should be noted that the flange 138 and the complementary groove 140 need not extend along the full width of the die body portion 104 as shown in Fig. 7 and that the lip adjustment block 132 may, in fact, be coupled to the lip 114 in any conventional manner known to those of ordinary skill in the art. The lip adjustment block 132 is provided with one or more slots or recesses 144 which are sized to closely receive the cam blocks 128 for sliding movement therein. A pull screw 146 extends through a rail end plate 148 mounted on the end 150 of the die 100 and is threaded into one end 152 of the sliding angle member 126. During operation, the sliding angle member 126 is moved longitudinally within the recess 130 by turning the pull screw 146. As the sliding angle member 126 moves laterally along the width of the extrusion apparatus 100, the cam blocks 128 are carried therewith and, in turn, engage the walls defining the recesses 144. This movement causes the lip adjustment block 132 to move in a direction shown by the arrow 154 of Fig. 5, i.e., perpendicular to the lateral movement of the sliding angle member 126. By keeping tight clearances between the various parts, precise movement of the lip 114 can be obtained, and the lip 114 can be secured in the desired position. Simultaneously, lip heaters (not shown) in thermal contact with the bolts 122 may be controlled so that the dimensions of the die outlet 120 can be precisely adjusted. An indicator pin 156 extends from the end 152 of the sliding angle member 126 and projects through a hole 158 in the rail end plate 148. The indicator pin 156 may be marked with a scale indicating the position of the lip 114. As should be evident from the foregoing, by making a simple, single-point adjustment (i.e., turning the pull screw 146), the entire lip 114 may be moved to adjust the lip gap 120. Further, by initially setting the position of the lip 114 at a mid-range position, a total travel range for the lip 114 of 0.200 inches (i.e., ± 0.100 inches from the mid-range position) can be achieved. Thus, the die outlet 120 can be preset to a wide range of gap widths in a relatively short period of time as compared with the prior art die designs described above. It should also be noted that instead of providing the disclosed manual or automatic adjustment of the lip 108, an alternative adjustment apparatus or any other moving means may be provided, as desired. In fact, the adjustment apparatus could be identical to that used to move the lip 114 as described herein. Alternatively, one or more servomotors may be employed in conjunction with a computer control to automatically adjust the positions of one or both lips 108, 114 in response to commands issued by an operator of the die 100, if desired. In addition, it should be noted that the lips 108, 114 may be separate from the main body portions and may be secured to the main body portions by means other than integral hinges. An alternative embodiment of the lip adjustment apparatus is shown in Figs. 8-10, in which elements that are also present in the embodiment of Figs. 5-7 are assigned the same reference numerals. In this embodiment, means 159 are provided at the end 150 of the die 100 for moving the lip 114 bidirectionally. The structure and operation of the lip adjustment block 132 and the sliding angle member 126 are the same in the alternative embodiment as in the embodiment described above. However, the pull screw 146 is replaced with a threaded stud 160 extending axially from one end of the sliding angle member 126 through a hole 162 formed in the rail end plate 148 and is received by a complementarily threaded spool 164. A spool retainer 166 is adapted for retaining the spool 164 to the rail end plate 148. The spool retainer 166 has a counterbore 167 that receives a complimentary flange 168 of the spool 164. Optionally, a cavity 169 may be formed in the rail end plate 148, the cavity 169 being so sized and shaped that the spool retainer 166 may be received within the cavity 169. The spool retainer 166 is bolted to the rail end plate 148, within the cavity 166 (if present), with a plurality of bolts 170. Referring now to Fig. 8, the operation of the alternative embodiment of the lip adjustment apparatus will now be described. The spool 164 may be rotated in either of first and second directions, i.e., clockwise and counter-clockwise, thereby causing the sliding angle member 126 to move laterally in respective third and fourth directions, i.e., into and out of the page as shown in Fig. 8. Consequently, the lip adjustment block 132, and thus the lip 114, are moved bidirectionally in response to rotation of the spool 164. An indicator 172 may be fastened to the lip adjustment block 132 to indicate the position of the lip 114. Of course, an alternative indicator, such as the indicator pin 156 of the first embodiment described above and shown in Figs. 4-7, may be used instead of the indicator 172. Further, the indicator 172, or any other suitable indicator, could replace the indicator pin 156 and the hole 158 in the embodiment of Figs. 4-7. The foregoing description is for the purpose of teaching those skilled in the art the best mode of carrying out the invention and is to be construed as illustrative only. Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of this description. The details of the disclosed structure may be varied without departing from the scope of the appended claims.

Claims: An extrusion apparatus for extruding a single stream of thermoplastic material, comprising: 1.1 first and second die body portions (102, 104) each including a main body (106, 112), a lip (108, 114), and a hinge (110, 116) interconnecting the lip (108, 114) and the main body (106, 112) wherein the hinge (110, 116) permits movement of the lip (108, 114) relative to the main body (106, 112) and wherein the first and second die body portions (102, 104) are joined together to form a die outlet (120) bounded on first and second sides by the lips (108, 114) of the first and second die body portions (102, 104), respectively, whereby the single stream exits the apparatus through the die outlet (120) in contact with the first and second lips (108, 114), and 1.2 moving means coupled to the lips (108, 114) of the first and second die body portions (102, 104) for moving the lips (108, 114) relative to one another to permit adjustment of the die outlet (120) to thereby control the thickness of the single stream of thermoplastic material, characterized by the following features: 1.3 the moving means including a lip adjustment block (132) coupled to one of the lips (116) for adjusting the position of the one lip (116) and further including translating means for translating the lip adjustment block (132); 1.4 the translation means including a sliding angle member (126) movable transverse to the direction of movement of the lip adjustment block (132); 1.5 such, that the said transverse movement of the sliding angle member (126) causes the lip adjustment block (132) to move in the desired lip adjustment direction. Extrusion apparatus according to claim 1, characterized by the following features: the sliding angle member (126) has a threaded stud axially extending therefrom and a spool threadedly engaging the stud wherein the spool is retained to one end of the die such that rotation of the spool in either of first and second directions causes lateral movement of the sliding angle member (126) in respective third and fourth directions thereby translating the lip adjustment block (132) to adjust, in turn, the position of the one lip (116) bidirectionally. An extrusion apparatus according to claim 1 or claim 2, directorized by the following features: 3.1 the sliding angle member (126) comprises cam blocks (128), and the lip adjustment (132) comprises recesses (144); 3.2 the said cam blocks (128) and the said recesses (144) are arranged such that upon movement of the sliding member (126) the lip adjustment block (132) moves in the desired adjustment direction.

Inventors: GARTON DONALD R, KRUPA VERNON J, LIPPERT HARRY G, RYAN JOHN W, WILSON GREGORY M, GARTON, DONALD R., KRUPA, VERNON J., LIPPERT, HARRY G., RYAN, JOHN W., WILSON, GREGORY M.
Applicants: EXTRUSION DIES INC, EXTRUSION DIES, INC.
Application year: 1994
Main classification: B29C47
IPC codes: B29C47